Reader map
What this page proves
Kinetic energy converted to rotor surface heat. Start here for the build, question, measurement, and closeout proof.
What we are making
A brake thermal test: aim patch, prediction sheet, stopwatch cadence, temperature table, cooling curve, and error budget.
Question answered
How close is a kinetic-energy temperature prediction to the measured rotor surface rise after a controlled stop?
What will be measured
Baseline rotor surface temperature, first post-stop reading, and 21 cooling readings over 10 minutes.
Proof that closes it
04_energy_prediction.pdf, 04_aim_patch_photo.jpg, 04_temperature_log.csv, 04_cooling_curve.png, 04_prediction_vs_measurement.png, 04_error_budget.pdf, and 04_summary.pdf.
A moving car has kinetic energy. Brakes turn that motion into heat. This test predicts how hot one rotor surface should get, then measures the same taped spot while it cools.
Words you need
Project terms
| Term | Meaning on this page |
|---|---|
| Kinetic energy | Energy from vehicle speed. |
| Rotor | Disc squeezed by brake pads. |
| Heat capacity | Energy needed to raise temperature. |
| Infrared thermometer | Surface temperature tool. |
| Emissivity | How strongly a surface emits infrared. |
| Baseline | Starting temperature. |
| Cooling curve | Temperature plotted against time. |
| Error term | Named reason prediction and reading differ. |
| Front brake bias | Front share of braking. |
| Thermal mass | Mass absorbing heat. |
| Uncertainty | Expected error range. |
Capstone framing
Objective, requirements, constraints
| Type | Specific requirement |
|---|---|
| Objective | Predict and measure rotor surface temperature rise. |
| R1 | Baseline stable within 2 C. |
| R2 | First reading within 10 s. |
| R3 | 21 cooling readings over 10 min. |
| R4 | Prediction documented before run. |
| R5 | Measured rise compared to prediction. |
| R6 | Error budget published. |
| Safety | Adult driver; closed course or empty legal site; observer records. |
Section 01 · Concept
Energy basis of the test
Braking converts kinetic energy to heat, most of it at the front axle. This study predicts the rise from a single 60→0 mph stop with pencil-and-paper physics, measures it, and reports the two numbers side by side.
What it is
Test summary
One 60→0 mph stop puts roughly 141 kJ into the front-left rotor under this sheet's assumptions. Within seconds of stopping, the thermometer reads how much hotter the rotor got. For the next 10 minutes, a reading every 30 s builds a handwritten table that becomes the cooling curve.
Everything is fixed before the run: where to aim (a taped patch), when to read (within 10 s), and what to expect (a prediction written down in advance). After the run, the measured number either confirms the prediction or shows which source of error mattered most.
Actual principle used
Kinetic energy converted to rotor surface heat
Three ideas run through the sheet: energy turning into heat, heat draining away over time, and careful measurement. Each one is tied to a specific number on this page.
Conversion
575 kJ at 60 mph
Into rotor
141 kJ assumed split
Cooling log
10 min
Cross-check
≈34 °C 60→0 mph
Section 04 · Sequence
Build sequence and gates
The order is: plan, mark, baseline, stop, log, analyze. Five pass/fail checkpoints (“gates”) spell out the evidence the study must produce.
Test conduct and where it leads
Safety and next steps
Runs happen on a closed or empty stretch at legal speeds, with the cooldown area picked before the first drive. Wheel chocks go in ahead of the first reading, and rotor handling waits until the 10-minute log shows the disc back near ambient.
A repeated-stop fade study is the follow-on: same aim mark, same cadence, higher starting temperatures each round. The 30 s logging rhythm practiced here carries into the OBD-II drive logger (build 02), which records the same kind of time series at about one reading per second.
Sequence
Test sequence
Plan. Select the closed course or empty legal stretch; define the 60→0 mph stop and a cooldown area off the travel lane.
Record. Write down the vehicle mass estimate with its source, ambient air temperature, wind conditions (calm, breezy, or gusty, and direction relative to the parked car), and front-left rotor access.
Mark. Tape the ~1.5 in aim patch on the rotor's unswept outer vane rim at full left lock, photograph it, and confirm it shows through the spokes with the wheel straight.
Baseline. Read the aim patch at the test site until three consecutive readings agree within 2 °C — the arrival drive leaves the rotor warm — then keep the brakes untouched until the test stop, positioning by coasting.
Stop. Execute the 60→0 mph stop in neutral at a firm, steady ~0.3–0.4 g without triggering ABS, shift to park on the rear-acting parking brake, and step out with the gun in hand to read the patch within 10 s. Chocks go in right after that reading; with a two-person crew, the observer waiting at the cooldown mark takes it.
Log. Read the aim patch every 30 s for 10 minutes into the handwritten table, noting any wind shift.
Analyze. Compute braking energy, plot the cooling curve, compare the measured temperature rise to the ≈34 °C prediction for the 60→0 mph stop, and size each error term with its sign.
Acceptance gates — owner: Kohler
Acceptance gates
Risk, judging, and closeout
What can fail and how the result is judged
What could go wrong
| Risk | Control | Failure action |
|---|---|---|
| Unsafe site | Closed course or empty legal site. | Cancel and move. |
| Driver distraction | Observer handles instruments. | Discard if driver touched device. |
| Surface vs bulk | State IR reads surface only. | Do not claim total rotor energy. |
| Bad emissivity | Use same tape patch. | Repeat if tape fails. |
| Late first read | Read within 10 s. | Repeat run. |
| Wind | Record conditions. | Flag or repeat. |
How the result will be judged
| Check | A-level result | Not acceptable |
|---|---|---|
| Prediction | Energy calculation saved before run. | Back-fit math. |
| Measurement | Baseline plus 21 timed readings. | Scattered readings. |
| Comparison | Measured rise plotted against prediction. | Only raw numbers. |
| Uncertainty | Mass, speed, bias, heat split, emissivity, delay, wind named. | Mismatch called mystery. |
Data package
Exact closeout filenames
- 04_energy_prediction.pdf
- 04_aim_patch_photo.jpg
- 04_temperature_log.csv
- 04_cooling_curve.png
- 04_prediction_vs_measurement.png
- 04_error_budget.pdf
- 04_summary.pdf
Senior capstone readiness
Current status: build plan; data pending. A-level requires repeat trials, measured rotor mass, emissivity control, cooling-model fit, and uncertainty propagation.
Definition of done
- Prediction is written before the run.
- Aim patch photo and baseline are saved.
- Temperature log covers baseline through 10:00.
- Cooling curve, comparison chart, and error budget are published.
Section 02 · Method
Aim patch and reading procedure
An infrared thermometer does not read a single point. It averages over a small circle, and the circle grows the farther away you stand — from 12 in, this gun reads a 1 in circle. A patch of painter's tape marks one aim spot on the rotor, and every reading in the log comes from that patch, taken from the same 12 in distance.
Test setup and cooling log · live model
Front-left rotor with caliper, IR beam on the taped aim patch, and the 30 s cooling log that follows the stop. Aim-patch photo is gate AIM-1.
Worked prediction
Predicted rise: 34 °C
KE = ½·m·v² = ½ · 1,600 · 26.8² ≈ 575 kJ for the whole vehicle — translational KE; aero, rolling, and driveline losses during the stop neglected, rotational KE excluded
Front axle ≈ 70% of braking → one front rotor ≈ 35% → 201 kJ
Assumption: 70% of that heat enters the rotor disc → 141 kJ — a deliberately conservative lower bound; the effusivity-based partition for cast iron on organic pads runs 0.85–0.95, which would give ≈44 °C
Rotor ≈ 9.0 kg cast iron · c = 460 J/(kg·K) → ΔT = 141,000 / (9.0 × 460) ≈ 34 °C — lumped bulk-average disc temperature (Bi = hL/k ≪ 1)
The reading taken within 10 s of stopping gets compared to the prediction of about 34 °C of rise. If the measured rise lands between 17 and 68 °C above baseline, checkpoint XCHK-1 passes. If it lands outside that band, the checkpoint fails, and the report names which error term in the table below caused the miss.
Aim patch and log cadence
Fixed aim patch
The aim patch is a ~1.5 in square of painter's tape on the outer rim of the rotor, about 6 in from the hub center, where the pads never touch. It goes on with the steering turned fully left, gets photographed, and then gets checked as visible through the wheel spokes with the wheel straight. If a closed-face wheel hides it, the wheel comes off for the run — jack, lug wrench, and torque wrench on reinstall.
Every reading lands on the tape itself, for a physical reason: tape gives off infrared strongly (emissivity ≈0.95), which matches the gun's fixed setting. Bare cast iron gives off infrared weakly and can read low by tens of degrees. Before the baseline reading, confirm the measurement circle sits fully on the tape.
Standoff is 12 in, marked on the gun with a tape flag or a string gauge. At that distance the gun reads a 1 in spot inside the 1.5 in patch. All 22 readings — the baseline plus 21 cooling points — repeat the same geometry.
Aim patch
taped + photo
First read
≤10 s
Cadence
30 s
Duration
10 min
Error terms — each named, each bounded
Error terms between prediction and reading
Each error source gets a name and a step that limits it. When the prediction and the measurement disagree, the write-up can say which term pushed the number which way, instead of calling the mismatch a mystery.
| Term | Bounded by |
|---|---|
| Convection during the measurement walk-up | TEMP-1 · first reading ≤10 s |
| Tape emissivity at the aim patch | AIM-1 · readings on the ≈0.95 tape only |
| Heat share into pads and caliper | 70% lower-bound assumption · sized in Step 7 |
| Through-thickness gradient at the first reading | cast iron equilibrates in ~10–15 s (L²/α, ~6 mm cheek) · a ≤10 s reading sits within a few °C of the bulk mean |
| Engine braking, aero, and rolling losses during the stop | neutral, firm ~0.3–0.4 g stop · no ABS |
| Friction ring holds the early heat while the 9.0 kg figure includes the hat | biases the 10 s reading high vs. the whole-disc ΔT · sized in Step 7 |
Zoo / SolidWorks — build this model
Rotor model and mass check
Model the rotor as one revolved part, sized from caliper measurements: outer diameter, thickness, hat depth, vane count. SolidWorks then reports the disc's volume, and volume times cast iron's density gives a better rotor mass than the estimate used on this page. A better mass tightens the 34 °C prediction before the test ever runs.
Produce one drawing of the disc with the aim patch marked 6 in from the hub center, on the unswept outer rim. The export macro turns it into the PNG used on this page. A working model of this build is embedded just below, and its STL download opens in SolidWorks, Onshape, or FreeCAD.
Runs in: Zoo (free — its Zookeeper agent builds from this prompt, edits by conversation, and answers design questions) · SolidWorks LEO · or by hand from the list above.
The Zoo file goes into the zoo-design-studio-projects folder shown at the top of Zoo’s Projects screen; the build then appears in the Projects list, dimensioned from this sheet. Paste the macro into SolidWorks (Tools → Macro → New) to export every drawing as a web image.
Model
revolved disc
Check
mass from volume
Drawing
aim-patch location
Works on
any tier
Section 03 · Parts
Parts and cost
Nearly all the cost is one instrument: a generic 12:1 D:S infrared thermometer in the $18–35 class (Etekcity or Klein grade). The Fluke 62 MAX costs $126 and reads a wider spot, so it sits above this sheet's budget. Everything else on the list is cheap hardware, already owned, taped on, or handwritten.
Bill of materials
Parts and materials
| Item | Qty |
|---|---|
| Vehicle with accessible front-left rotor | owned |
| Infrared thermometer, generic 12:1 D:S optics, $18–35 (Etekcity/Klein class; the Fluke 62 MAX is a $126, 10:1 instrument and stays off this list) | 1 |
| Thermometer for ambient air, $5–10 — an IR gun reads surfaces, never air | 1 |
| Stopwatch or phone timer | 1 |
| Phone or camera for the aim-patch photo | owned |
| Wheel chocks | 2 |
| Painter's tape for the aim patch | roll |
| Marker, clipped to the notebook log pad | 1 + pad |
| Heat-resistant gloves for wheel-well work | pair |
| Hi-vis vest, worn from the stop through the last reading | 1 |
| Jack, lug wrench, torque wrench — for a closed-face wheel that hides the aim patch | owned |
| Marker and pen for the aim point and the handwritten log | $3–5 |
| Lug wrench or breaker bar + torque wrench, for wheel removal where the wheel blocks the aim point (owned) | $0 |
| Parts total | $50–95 |
Tools and environment
Tools and test conditions
An IR thermometer, an air thermometer for the surrounding air, a stopwatch or timestamped recording, a phone for the aim-patch photo, and a written source for the vehicle's weight. Closed-face wheels add the car's own jack, lug wrench, and torque wrench, because the tape patch has to be visible within 10 s of stopping. Driving happens on a closed course or an empty, legal stretch, with a cooldown spot off the travel lane picked in advance.
Time
12–20 h
Cost
$50–95
Optics
12:1 D:S
Shop tools
jack kit if wheel hides aim
Section 05 · Scope
Scope and next steps
The scope is small on purpose: one rotor, one stop, one cooling curve, one comparison. A natural follow-on repeats the stops back-to-back to watch the brakes “fade” as they heat up, and this single-stop study is the starting point for it.
Evidence package
Four deliverables
One folder holds it all: the temperature table, the plotted cooling curve, the energy calculation with its assumptions, the error notes, and the aim-patch photo.